Health-related quality of life in patients with hip or knee osteoarthritis: comparison of generic and disease-specific instruments.

Health-related quality of life (HRQL) assessment is receiving increased attention as an outcome measure in osteoarthritis (OA). The aims of the study were to assess the health status impact of hip and knee OA in the general older population and to compare the metric properties of the WOMAC disease-specific questionnaire (Western Ontario and McMaster Universities) with generic measures [i.e., the Short Form 36 (SF-36) in patients with OA of the lower extremities]. This cross-sectional survey included a total of 244 patients (99 male, 145 female), aged 50 years and over, with symptomatic OA of the hips (107 patients) and knees (137 patients). All patients completed the WOMAC and the SF-36 questionnaires and were assessed for radiographic damage and for the presence of specific comorbid conditions. The overall impact on health was substantial for both groups of patients with OA of the lower extremities. The most striking impact was seen in OA of the hip for SF-36 "physical function" (p=0.03) and "physical role" (p=0.04), as well as WOMAC "physical function" (p=0.001). Furthermore, impairment of HRQL was only weakly associated with increasing radiographic changes. The SF-36 overall scores showed a better gradient with comorbidities than the WOMAC. This investigation has confirmed that WOMAC is the instrument of choice for evaluating patients with lower limb OA. For a more general insight into patient's health and in particular cross-sectional studies of the elderly, where comorbidity is common, the SF-36 should also be used. This study also provides an estimate of the impact of OA of the hip and knee on HRQL.